Like find someone and just ask them to join? That would be pretty interesting! I made the costumes to give the feeling you now belong to their faction but I havent deepened that feeling of belonging yet. You kinda just play with a new skin right now.
I was thinking on giving objectives to the player to progress in the faction but I need to finish a dialogue system first. And then if the player finished the objectives they would unlock or get a special outfit as a reward.